== Summary ==
When creating a srcdoc document, we need to be careful to avoid
introducing a Content-Security-Policy loophole.
== Details ==
Consider a document with the following Content-Security-Policy:
Content-Security-Policy: default-src 'none'; frame-src *
Now, imagine the following injection vulnerability in index.php:
<body>Hello <?=$username?></body>
This Content-Security-Policy is supposed to prevent the attacker from
being able to inject script into index.php. However, consider the
following value for $username:
$username = '<iframe
srcdoc="<script>alert(parent.document.cookie);</script>"></iframe>';
In this case, we could get in trouble if the user agent doesn't
enforce the parent document's Content-Security-Policy on the srcdoc
document because the user agent copies the parent document's origin
unto the child document.
== Proposal ==
When creating a srcdoc document, in the same way that we copy the
parent document's origin onto the child document, we should:
1) /enforce/, on the srcdoc document, all CSP policies currently being
enforced on the parent document.
2) /monitor/, on the srcdoc document, all CSP policies currently being
monitored on the parent document.
Please see <http://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html>
for definitions of these terms.
Thanks!
Adam